1. Field of the Invention
This invention relates to a self-positioning refractory structure, preferably having a circular cross-section and particularly for a generally circular air-cooled incinerator afterburner.
2. Description of the Prior Art
Existing furnace wall constructions that have a space between the cold side of the refractories and a casing wall or other structural support use complex arrangements of structural steel to support the refractories. Most often, castings, I-beams, clamps, and other specially fabricated structural components are used to suspend the refractories from a furnace roof or furnace wall.
A common method of incinerating hazardous waste is to use a rotary kiln with an afterburner. Hazardous waste is charged into the rotary kiln and tumbles causing the waste to release most of its heat content. Product gases enter an afterburner and must be burned at up to 2200.degree. F., according to environmental regulations, with a one or two second retention, depending upon the type of hazardous waste or other waste. Such afterburners have either a rectangular or generally circular cross section. Round afterburners are constructed with either monolithic materials or brick. Most brick constructions use straight-sided wedge shaped bricks which are installed in rings and suspended from structural shelves. Insulation is also normally installed in the afterburner. According to the prior art, cooling the wall behind such types of refractory with air flow is virtually impossible since the brick tends to move toward the casing thus eliminating any available space for air flow between the refractories and the casing wall.
High temperature furnaces may include a curved wall portion known as a fantail turn or nose construction which makes the transition between a vertical or angled wall and a suspended horizontal roof, or between two walls having some other angular relationship to each other. Existing fantial turn or nose construction designs use refractories suspended from the cold side of a furnace with at least each pair of refractories requiring a suspension hanger. Such construction designs create a maze of suspension hangers. Existing nose constructions generally comprise a plurality of wedge-shaped refractories having a generally planar front, back and opposing sides which converge toward the cold side of the nose construction, as taught by U.S. Pat. Nos. 1,636,603, 1,764,707, 2,132,517, 2,272,015 and 2,685,264. U.S. Pat. No. 1,582,275 teaches a curved construction having hanger refractories with planar surfaces which converge toward the cold side and filler refractories with planar surface which converge toward the hot side.
U.S. Pat. No. 4,463,689 teaches a high temperature furnace nose construction providing refractory replacement from the cold side of a furnace. A plurality of wedge-shaped refractories and a plurality of rectangular-shaped refractories are arranged to form straight rows along the length of the nose construction. Both the rectangular-shaped and wedge-shaped refractories have planar sides and require a hanger to suspend two adjacent refractories.
U.S. Pat. No. 3,958,519 teaches high temperature furnace construction for flat roofs and walls using refractories having interlocking corrugations. Merkle Engineers, Inc. has used and sold for several years the rectangular filler and hanger refractories as described in the '519 patent. Merkle Engineers, Inc., P.O. Box 312, Galena, Ill. 61036, has published catalog brochures entitled "MODU-LOK" and "Suspended and Tied Back Refractory Systems for Incineration and Resource Recovery Projects" describing these rectangular filler and hanger refractories.
U.S. Pat. No. 1,710,901 discloses a furnace wall construction suspended from structural support members within a refractory wall. Rectangular refractories have T-slots for engagement with retaining flanges of hangers secured from the structural members. Reduced portions of the refractories leave vertical channels which extend through the wall and open into an air chamber. Each refractory of the furnace wall construction is suspended by a hanger.
U.S. Pat. No. 1,789,074 teaches a furnace wall construction having upright supporting members which structurally support holding plates and lining of the furnace wall. Angle braces provide further support between the upright supporting members and supporting plates adjacent to the lining.
U.S. Pat. No. 2,446,766 discloses a supported furnace arch or roof construction. The refractory members are suspended from crossbeams with metal hanger members and refractory hanger members. The crossbeam members are supported from main I-beams with clips.
U.S. Pat. No. 2,524,722 discloses a roof or arch construction for a furnace. A plurality of suspension tiles and roof tiles are suspended from brackets secured to I-beams which are disposed at right angles to another structural I-beam which is secured to a vertical I-beam post. Insulation may be disposed on the roof tiles and filler tiles. The filler tiles are supported by the roof tiles.
U.S. Pat. No. 2,634,694 discloses a suspended arch tile structure having face tiles suspended from hanger bricks which are suspended from channels or arches. The channels or arches are clamped to a structural beam by suitable clamping brackets. Intermediate tiles are supported by the face tiles.
U.S. Pat. No. 2,664,836 discloses a suspended roof structure having intermediate blocks supported by suspended blocks. The suspended blocks are supported by stringers which comprise channel beams. The stringers are suspended from a steel beam by fastening plates.
U.S. Pat. No. 2,870,624 discloses a furnace wall having a series of horizontal support bars bolted to inner faces of columns. Tile blocks are suspended from the support bars with high temperature alloy tile supporting hangers.